Questions tagged [virtual-machines]
A virtual machine (VM) is a completely isolated guest operating system installation within a normal host operating system. It is a software implementation of a machine (i.e. a computer) that executes programs like a physical machine.
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Is it possible to make Nginx listen to different ports?
I created one Nginx with one Linux Azure VM, is it possible to make nginx listen to different ports so that when I change the port number, the content would be different. I found there would be a ...
133
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answers
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Why do we use a OS Base Image with Docker if containers have no Guest OS?
I've just started to study Docker and there's something that's being quite confusing for me. As I've read on Docker's website a container is different from a virtual machine. As I understood a ...
101
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What range of MAC addresses can I safely use for my virtual machines?
I want to assign my virtual machines MAC addresses so that I can configure DHCP reservations for them so that they always get the same IP address regardless of which host hypervisor they are running ...
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16
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How do I know if I'm working on a Virtual Machine or not?
Is there a way to know if the Windows machine I'm working on is virtual or physical?
(I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).
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Is a VM with 2 CPUs really faster than one with 4 CPUs?
Our IT created a VM with 2 CPUs allocated rather than the 4 I requested. Their reason is that the VM performs better with 2 CPUs rather than 4 (according to them). The rationale is that the VM ...
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9
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Creating a virtual machine in VirtualBox from a physical one
Is there any way to create a virtual machine that you can use in VirtualBox from a physical installation that you have? For instance, if I have Windows XP installed on a physical computer and want to ...
34
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12
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Is it possible to setup a virtual machine inside another virtual machine
I've been playing with virtual machines lately, and I wondered if I could run a virtual machine inside a virtual machine. Is this possible? Is it practical?
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Why VM snapshots are affecting performance?
I read in one of the VMware KB articles that snapshots will directly affect VM performance.
But my team keeps asking me how snapshots can affect performance.
I would like to give them solid reason ...
27
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1
answer
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KVM and Libvirt - How do I hotplug a new virtio disk?
I am trying to hot-add a file-based disk to a running KVM virtual server. I've created a new disk from scratch using the command
dd of=/home/cloud/vps_59/test.img bs=1 seek=5G count=0
and I was ...
27
votes
4
answers
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Will virtualizing a server mean another OS layer to patch and update, more work and greater risk?
I've done a search and have not found anything addressing issues regarding patching and system updates. I've got guidelines that say servers need to have necessary patches. If I have a VM host then ...
26
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7
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mount.nfs: access denied by server while mounting
On my Ubuntu system, I have this line in /etc/fstab:
myserver:/home/me /mnt/me nfs rsize=8192,wsize=8192,timeo=14,intr
When I do
sudo mount -a
I get:
mount.nfs: access denied by server while ...
26
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1
answer
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Why Are There Only 65,535 Ports, and Will We Ever Have More? [closed]
I understand the original reasoning behind having 65,535 ports per IP address: this is the highest number that can be represented by a 16-bit, or 2-byte, number, and it wasn't conceivable that ...
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answers
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Is there a reason to give a VM a round base-2 amount (2048MB, 4096MB, etc) of memory?
The title pretty much says it all, is there any advantage to giving a VM 2048MB of memory instead of rounding to base-10 and doing 2000MB?
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answers
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Running 100 virtual machines on a single VMWare host server
I've been using VMWare for many years, running dozens of production servers with very few issues. But I never tried hosting more than 20 VMs on a single physical host.
Here is the idea:
A stripped ...
25
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2
answers
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When shall I use linked vs full VM clones?
I've seen documentation for the Full and Linked virtual machine clones, but I can't seem to fully understand when I should use one over another. I see that the full clone creates a copy of the VM, but ...
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Sync LVM snapshots to backup server
I have a number of Xen virtual machines running on a number of Linux servers. These VMs store their disk images in Linux LVM volumes with device names along the lines of /dev/xenVG/SERVER001OS and so ...
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Virtualization Pitfalls/Lessons Learned
What are some pitfalls or lessons learned after converting existing hardware to a virtualized environment? Is there anything you tried to virtualize but will never do again?
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Is it safe to mount the same partition to multiple VMs?
I'm using ubuntu 20.04 with Xen Hypervisor. On my machine I have an SSD that hosts my VM images, and then four sata drives which I have data on. My current set up is to mount the data on my domain0 ...
22
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3
answers
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Cloning Virtual Machine On Azure, keeping existing
There doesn't seem to be a straight answer online about this. I have an existing Virtual Machine on Azure and I want to clone it to another region in case my existing server goes down. It needs to be ...
21
votes
4
answers
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Why do cloud compute instances spin up VMs and not containers?
In AWS for example, when I spin up a new EC2 instance, it loads up a new VM, then populate the VM with a container image. This is the reason why spinning up new EC2 instances take 60-90 seconds to ...
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6
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How to attach a virtual hard disk using VBoxManage?
What is the best method for setting the virtual hard drive (VDI) of the primary controller for an existing virtual machine?
Does the syntax change if the VDI is really a child differencing disk of ...
21
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6
answers
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How do I get /dev/random to work on an Ubuntu virtual machine?
Apparently, /dev/random is based on hardware interrupts or similar unpredictable aspects of physical hardware. Since virtual machines don't have physical hardware, running cat /dev/random within a ...
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2
answers
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understanding relationship between Qemu and KVM
What is the difference between KVM and Qemu? As I understand, latter is able to provide "user mode emulation" which means that one can run a single executable built for some other architecture like ...
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So really, what is the overhead of virtualization and when should I be concerned?
I'm searching for good rules of thumb to understand when NOT to virtualize a machine.
For example, I know that a fully CPU-bound process with near 100% utilization is probably not a good idea to ...
19
votes
5
answers
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Can a VMWare Server 2.0 virtual machine be "unvirtualized" to physical hardware?
We have a number of VMWare Server 2.0 virtual machines that were created using VMWare Converter (It copies a physical machine to a virtual machine). If we need to convert the virtual machine back to a ...
18
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5
answers
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Is there a way to have a virtual machine only have one core yet use three cores on the host machine? [duplicate]
Possible Duplicate:
Can a single Virtual Core on a VM use more then 1 physical core?
I'm a co-owner of a Minecraft server that is getting rather large each day, but as we get bigger we're running ...
18
votes
9
answers
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Hyper-V vs. ESXi vs. XenServer
Can anyone share their experiences (for example, this was great! This failed miserably!) with using the Hyper-V, ESXi, and XenServer virtualization platforms? Cost? Management? features? Handling load ...
17
votes
3
answers
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How is memory allocated in ESXi server?
We have an ESXi 4.1 server with 48 GB RAM.
For each VM, we are allocating 4GB of memory. Since the server will have 13 virtual machines, my manager thinks this is wrong.
I am going to explain to ...
16
votes
7
answers
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How to setup /etc/issues to show the IP address for eth0
I've got a couple of linux virtual machines with bridged interfaces, and I'd like the IP address of the machine to show up after the machine boot (in the login, where it usually shows the release and ...
16
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5
answers
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Defrag in Windows VM?
I've read conflicting advice on this issue so thought I'd ask here.
Should I be running a scheduled defrag within my VM?
16
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3
answers
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PING icmp open socket: Operation not permitted in vserver
I am running a vserver environment with several virtual machines. A single VM has the following problem:
$ ping 8.8.8.8
ping: icmp open socket: Operation not permitted
$ ls -l $(which ping)
-rwsr-xr-...
16
votes
3
answers
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MSTSC: Black Areas on Remote Desktop
I'm connecting from Windows Server 2012 R2 to Hyper-V virtual machine running Windows 8.1 via RDP (mstsc.exe). The VM is hosted on the same machine from which I'm connecting.
Everything was fine until ...
16
votes
2
answers
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Running containers inside a virtual machine?
It is my understanding that containers are much more lightweight than VMs because they do not virtualize the hardware but instead just isolate the software running in them from software running in ...
16
votes
4
answers
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Vagrant shared folder and file change events
I have ubuntu virtual machine that I'm accessing through Vagrant.
On my host (Mac OSX), there is a folder with couple of files, that I share to virtual machine. In that virtual machine, I want to use ...
16
votes
2
answers
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Renaming an Azure VM
I am looking to rename an Azure VM. I have copied a VM from one subscription to another using this guide:
http://blogs.msdn.com/b/microsoft_press/archive/2014/01/29/from-the-mvps-copying-a-virtual-...
15
votes
15
answers
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Web based KVM management for Ubuntu
We've got a single Ubuntu 9.10 root server on which we want to run multiple KVM virtual machines. To administer these virtual machines I'd like a web based KVM management tool, but I don't know which ...
15
votes
2
answers
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Running Mac OS X on Hyper-V
I have my workstation setup with a Windows Server 2008 running Hyper-V.
Now I really want to install OS X for testing purposes.
Have anyone had any success running Mac OS X in an Hyper-V environment?
...
14
votes
5
answers
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virsh: VM console does not show any output
I have a VM which I can start with virsh. According to virsh dumpxml VM1, this is the allocated pty:
<serial type='pty'>
<source path='/dev/pts/6'/>
<target port='0'/>
<...
14
votes
2
answers
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How to get free space from mounted drive Redhat 7
In our VM infrastructure, we have clustered hosts going to a SAN.
What i am trying to figure out is how much "white space" is left over when deleting files within our Redhat servers. On our Windows ...
14
votes
6
answers
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How to decrease the size of a KVM virtual machine disk image?
How do you decrease or shrink the size of a KVM virtual machine disk?
I allocated a virtual disk of 500GB (stored at /var/lib/libvirt/images/vm1.img), and I'm finding that overkill, so now I'd like ...
13
votes
11
answers
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Any way to run Linux as a Virtual Machine on top of Windows so can have best of both worlds?
Since Linux has a lot of useful tools, while Windows has a lot of apps (like Chrome), instead of buying another machine to run Linux, is there a way to run it as a Virtual Machine on the PC? The ...
13
votes
5
answers
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Renting a dedicated, but getting a VPS. How to detect? [duplicate]
When renting a dedicated server, how can one be certain than he/she is not getting a VPS or some other virtual machine variant instead of a true dedicated hardware box?
Which checks can be run (...
13
votes
8
answers
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What is this server doing?
I have a bunch of linux virtual servers left over from a previous IT department. They have names like 'magic' or 'stuff'. I'm not quite sure what they're doing...or if I need them...
How would you ...
13
votes
4
answers
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Can a virtual machine (VM) "hack" another VM running on the same physical machine?
Questions:
if a VM is corrupted (hacked), what do I risk on others VMs running on the same physical machine?
What kind of security issues is there between VMs running on the same physical host?
Is ...
13
votes
4
answers
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Is it dangerous to change the value of /proc/sys/net/ipv4/tcp_tw_reuse?
We have a couple of production systems that were recently converted into virtual machines.
There is an application of ours that frequently accesses a MySQL database, and for each query it creates a ...
13
votes
4
answers
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Backing up qcow2 kvm guests
I can't find any good info on backing up qcow2 kvm guests. I'm not really interested in the guests running state, only the file system. This question suggests using savevm but that creates a snapshot ...
13
votes
2
answers
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Entropy on virtual machines
As you might know that it's not as easy to generate entropy on a virtual machine as on a "normal" pc.
Generating a gpg-key on a virtual machine can take a while, even with the correct tools.
There ...
13
votes
3
answers
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Having Mac OS X on a XEN virtual machine
Is it possible to have Mac OS X guest on a XEN host?
If yes, how?
There are difference for Mac OS X Server?
In particular I'm interested in the installation of a testing Mac OS X Server inside a ...
12
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2
answers
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Windows Server 2008 R2 64-bit memory leak
I´m having trouble in one of my office servers. It´s a virtualized Windows 2008 R2 Server with 6GB RAM memory. It only has Microsoft SQL Server (memory assigned maximum = 3GB), and just a software ...
12
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4
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What happens when a physical machine fails in a virtual environment? [closed]
I'm getting started with virtualization so bear with me.
In virtual environments applications run in a hypervisor's layer. So a single physical machine could have many virtual machines on it running ...